1. Field of the Invention
This invention relates to a method for marking an indication on plastic lenses for eye-glasses.
2. Description of the Prior Art
The plastic lenses (hereinafter referred to only as lenses) are made of polymethylmethacrylate, polystyrene, polycarbonate, cellulose-acetate, diethylene glycol bis allyl carbonate, referred to hereinafter as CR-39, etc., and those lenses are widely used because of their excellent characteristics, such as light weight, shock resistance, heat resistance and solvent resistance.
In the prior art for marking such lenses, there are methods such as printing an indication on the lenses. However, such methods provide an unacceptable appearance, engraving on the lenses, high cost, the long time required to apply such works, easy peel-off of the printed indication and damage the lenses.
The present inventors have been making efforts to solve such drawbacks and to provide an easy method for marking the indication on such a plastic lens which is noticeable first when exposed to ultraviolet rays.